Field of the Invention
This invention relates generally to the field of wireless communication. In particular, the invention relates to Multiple Input Multiple Output (MIMO) antenna implementations capable of improved data throughput performance for use in such wireless communications.
Description of the Related Art
Commonly owned U.S. Pat. No. 7,911,402 describes a beam steering technique wherein a single antenna is capable of generating multiple radiating modes; the entire contents of which are hereby incorporated by reference. The multiple modes are effectuated with the use of offset parasitic elements that alter the current distribution on the driven antenna as the reactive load on the parasitic is varied. This beam steering technique where multiple modes are generated is referred to as a modal antenna technique, and an antenna configured to alter radiating modes in this fashion will be referred to here as a modal antenna.
A receive diversity application using modal antennas as described in commonly owned U.S. Ser. No. 13/227,361, filed Sep. 7, 2011, and titled “MODAL ANTENNA WITH CORRELATION MANAGEMENT FOR DIVERSITY APPLICATIONS”; wherein a single modal antenna can be configured to generate multiple radiating modes to provide a form of switched diversity; the entire contents of which are hereby incorporated by reference. Certain benefits of this technique include the reduced volume required in the mobile device for a single antenna instead of a two antenna receive diversity scheme, reduction in receive ports on the transceiver from two to one, and the resultant reduction in current consumption from this reduction in receive ports.
With MIMO (Multiple Input Multiple Output) systems becoming more prevalent in the access point and cellular communication fields, the need for two or more antennas collocated in a mobile device or small form factor access point are becoming more common. These groups of antennas in a MIMO system need to have high, and preferably, equal efficiencies along with good isolation and low correlation. For handheld mobile devices the problem is exacerbated by antenna detuning caused by the multiple use cases of a device: hand loading of the cell phone, cell phone placed to user's head, cell phone placed on metal surface, etc. For both cell phone and access point applications, the multipath environment is constantly changing, which impacts throughput performance of the communication link.